Brugia malayi is a human filarial infection, which can grow in mice. The PI hypothesizes that resistance of Brugia malayi is composed of an initial B dependent, T independent protective immune response which constrains initial parasite growth and that a subsequent T dependent, IL-4 mediated defense results in subsequent more effective immunity. The PI will use a combination of mice, genetically deficient in specific aspects of their immune response, and the adoptive transfer of specific cell populations into deficient mice, to investigate the mechanisms of the postulated immunoprotective events. The PI suggests that if B cells are important in this model, they may also be important in human disease and the specific modulation of their responses by B dependent immunogens may form a basis of an immunoprophylactic vaccine for humans.